An Ultimate Guide to Gastornis: The Stomach Bird

Leave a comment / / Updated on: 20th October 2023

Name MeaningGaston’s bird Height2 meters (6.6 feet)
EraCenozoic – PaleoceneWeight175 kilograms (386 pounds)
ClassificationDinosauria, Aves & GastornithiformesLocationEurope, Asia, North America

Gastornis Pictures

The Gastornis

Gage Beasley Prehistoric's Gastornis Concept
Gage Beasley Prehistoric’s Gastornis Concept

Sixty million years ago, our world was dominated by tropical and subtropical forests. 

If we were to go back to that habitat, we’d see Gastornis, a large flightless bird, walking leisurely through the forested areas.

Naturally, it was among many other prehistoric creatures!

Gastornis roamed through European, Asian, and North American forests. 

It was tall, had long legs, a massive skull, and a huge beak. Its wings were highly undeveloped, almost unnoticeable.

Its fossils were first discovered in the 19th century. 

Since then, paleontologists have unearthed multiple remains that have brought to light fascinating details about these prehistoric birds.

Read on to discover them!

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Physical Characteristics

Gage Beasley Prehistoric's Gastornis Size Comparison Chart
Gage Beasley Prehistoric’s Gastornis Size Comparison Chart

Gastornis birds were large, reaching almost 2 meters (6.6 feet) in height and 175 kilograms (386 pounds) in weight!

The weight is almost twice that of the common ostrich, often regarded as the largest extant bird! 

The common ostrich is 1.75–2.75 meters (5.7–9 feet) tall but weighs only 90–130 kilograms (198–287 pounds). 

As you’ve probably noticed, while the two have roughly the same height, Gastornis was much heavier, partly because of its massive skull and vertebrae!

If you observe a reconstruction, you instantly notice that it had a huge beak that was tall and flattened from side to side.

Its small nostrils were close to the front of the eyes. 

Gastornis, in all its glory | Aunt_Spray via Getty Images

The neck was short but had massive vertebrae, which ensured that the neck could support the large skull.

The wings were so small and reduced that they were almost unnoticeable. 

Gastornis wings are often compared to cassowary wings, which have only five or six large remiges (pennaceous feathers located on the wings) and are reduced to keratinous quills with no barbs.

Considering that Gastronis shares so many similarities with ratites like cassowaries, it’s unsurprising that it has often been portrayed as covered in hair-like plumage.

In reality, scientists aren’t completely sure of its plumage, as only one fossilized feather was discovered. 

Drawing of probable Gastornis feather from the Green River Formation. | Darren Naish via The Field Museum (CC BY-SA 3.0)

It was 24 centimeters (9.4 inches) long, broad, and vaned, making it similar to a flying bird’s feather.

Some Gastronis restorations depict it as having whitish, gray, and blue feathers, while others portray it as a black-and-yellow bird. 

The truth is, we’ll never know unless other fossils are discovered.

Besides this, only a few feathered prehistoric creatures served as subjects for studies focused on restoring plumage coloration. 

As such, this aspect of our world’s prehistory remains largely in the shade.

Habitat and Distribution

Although Gastornis birds probably originated in Europe, they acquired a much wider distribution over the years, as they migrated to North America and Asia.

Here’s where Gastornis lived:

  • Meudon, Paris, France
  • Berru, France
  • Provence, France (egg discovery)
  • Messel, Germany
  • Wasatch Formation, New Mexico, United States
  • New Jersey, United States
  • Willwood Formation, Wyoming, United States
  • Possibly Henan, China
  • Possibly Chuckanut Formation, North America (based on footprint discoveries)
  • Green River Formation, Roan Creek, Colorado, United States (feather discovery)

The distribution of Gastornis may have exceeded the territories mentioned above. 

We may never truly know how widely distributed they were.

After all, they spread from Europe to North America and Asia, didn’t they?

Fossils of Sabalites campbelli palm leaves from the Chuckanut Formation, south of Bellingham, Whatcom County, Washington | Murderbike via Wikipedia

Some theories imply that Gastornis reached Asia and North America through the Turgai Strait, which separated Europe from Asia, and the Bering Land Bridge.

Imagine what a long trip that was!

During the Paleocene, the climate was tropical or subtropical, depending on the regions, and temperate at the poles. 

The average global temperature was 24-25 degrees Celsius (75-77 degrees Fahrenheit).

Numerous plants thrived in this environment, and the world was dominated by coniferous and broad-leaved forests. 

Coniferous forest | DKart via Getty Images

Angiosperms were at the peak of development as well, especially since precipitation levels increased during the Paleocene.

The Eocene is known to have had the warmest period of the Cenozoic. 

Approximately 49 million years ago, however, our world experienced a transition to a cooling climate. 

Like the Paleocene, the Eocene was dominated by forests.

Can you imagine that palm trees grew even in Alaska and northern Europe?

Behavior and Diet

Life restoration of G. steini (now G. gigantea) with outdated, ratite-like plumage, 1917 | Photo via Matthew, William Diller, et al., 1917

As mentioned, Gastornis was a flightless bird. Instead, it may have been an agile runner, considering how long and robust its legs were.

On the other hand, it was not agile enough to be a predator of various fast-moving prey, which is why scientists ruled out the possibility of a pursuit predation technique. 

They suggested that if Gastornis were indeed a predator, it would have relied on an ambush technique. 

Other theories suggest that these flightless birds hunted in packs.

Still, scientists aren’t yet entirely sure it was a carnivore.

After all, it had a huge beak, which may have been used to crop tough vegetation or crack nuts and seeds. 

Look at that beak! | Aunt_Spray via Getty Images

Or it may have been used to subdue prey and even crack open bones.

Or it may have been used for both purposes.

Either way, even if it did eat plants once in a while, it probably wasn’t a pure herbivore, as its strong jaws and massive skull were not characteristic of a herbivorous diet. 

As such, some specialists argue that it was an omnivore, which is a safe assumption considering that there are arguments in favor of both herbivory and carnivory.

Still, a study published in 2014 showed that Gastornis was a pure herbivore because its reconstructed jaw musculature resembled that of extant herbivorous birds.

Life Cycle

Life restoration of G. gigantea, a species found in North America | El fosilmaníaco via Wikipedia (CC BY-SA 4.0)

Like modern birds, it reproduced by laying eggs.

This is proven by the discovery of large eggs in Provence, France, thought to have been laid by Gastornis

They measured 24 x 10 centimeters (9.5 x 3.9 inches).

Just imagine how huge they were!

The shell alone was 2.3-2.5 millimeters (0.09-0.1 inches) thick!

Apart from this, little is known about the reproductive behavior and ontogeny of Gastornis

Restoration and size comparison | Tim Bertelink via Wikipedia (CC BY-SA 4.0)

Luckily, we can turn to what is known about the extant birds’ reproductive system, assuming that at least parts of the details were valid for Gastornis and other prehistoric birds.

Male modern birds have a penis and two testes, while most females have a single ovary and a single oviduct. 

This means they lay only one egg at a time.

The eggs have hard shells made of calcium carbonate and are typically laid in nests. 

Once the last egg is laid, the female, the male, or both start the incubation process, which lasts between ten and 80 days, depending on the species.

Evolution and History

Skull and mandible of G. gigantea specimen AMNH 6169 | Matthew, William Diller via American Museum of National History

It is widely believed that birds are members of the Maniraptora group of theropod dinosaurs. 

Historically, scientists could outline a clear distinction between birds and non-birds. 

Everything changed when feathered dinosaurs were discovered, as they closely resembled birds.

Archaeopteryx remains are known for being transitional fossils outlining both reptilian and avian bird characteristics, thus indicating they were close relative of the true ancestor of modern birds. 

Somewhere on the lineage between the true ancestor and the modern bird stands Gastornis, which evolved and lived from the Paleocene until the Middle Eocene.

An illustration of Gastornis | Aunt_Spray via Getty Images

It is classified under the Gastornithiformes order of flightless fowl. 

Before this, Gastornis and the other members of this group were thought to have been part of the crane-like bird order Gruiformes. 

Further studies show they were part of the lineage that gave rise to screamers and waterfowl.

The first Gastornis fossils were described in the 19th century and named Gastornis parisiensis

The partial skeleton had been discovered by Gaston Planté, a French physicist, near Paris, France. 

Reconstructed G. geiselensis skeleton | DagdaMor via Wikipedia (CC BY-SA 4.0)

Over the years, paleontologists found other specimens that gave rise to several new species:

  • Gastornis gigantea
  • Gastornis sarasini
  • Gastornis geiselensis
  • Gastornis russeli
  • Gastornis xichuanensis
  • Gastornis laurenti

As occurs with many prehistoric animal species, the names mentioned above were not the first.

Gastornis gigantea, for example, was initially called Diatryma gigantea and included multiple specimens discovered primarily in the United States. 

Furthermore, Gastornis xichuanensis was initially named Zhongyuanus xichuanensis but was subsequently moved to the Gastornis genus.

Interactions with Other Species

Two Gastornis fighting over a nested territory. | Aunt_Spray via Getty Images

It would be impossible to imagine the multitude of animals Gastornis interacted with, especially since scientists aren’t sure of its diet. 

If it were a pure herbivore, it may have competed for food with other herbivores, at least in North America and Asia, because Europe probably did not have larger herbivores than Gastornis.

If it were a predator, what kind of prey would it prefer?

Reptiles, small mammals, insects, or arachnids?

We’d be glad to share the answer if we had it! 

Besides this, even if scientists confirmed its predatory behavior, food preferences probably would have depended on each individual’s geographic location.

Gastornis, an extinct genus of large flightless birds | Aunt_Spray via Getty Images

To outline a possible ecosystem that it was part of, we analyzed the fossil data from some formations that revealed Gastornis fossils. 

We created a list of animals it may have crossed paths with:

  • Primates
  • Artiodactyls
  • Bats
  • Perissodactyls
  • Hyaenodonts
  • Eutherians
  • Ungulates
  • Theriiformes
  • Reptiles
  • Fish
  • Invertebrates
  • Other birds
  • Crocodilians

The species Gastornis interacted with also depended on each bird’s temporal range. 

Besides this, since they’re known to have migrated from Europe to other continents, who knows what and how many animals they encountered on the way toward a new land?

Cultural Significance

Skeleton of Gastornis giganteus, a large flightless bird from the Eocene found in Wyoming. | Vince Smith via Flickr (CC BY-SA 2.0)

Although it was not the largest prehistoric bird, Gastornis is of major interest to scientists, especially in terms of diet, distribution, and possible predatory behavior.

For the past 200 years, paleontologists and other field-related specialists from around the world have been concerned with unearthing, identifying, and describing Gastornis fossils. 

Even after such extensive research, many details remain unknown, which isn’t so uncommon in paleontology after all!

Luckily for wildlife enthusiasts, Gastornis is quite popular in the media. 

This is excellent news, as media productions are perfect at making prehistoric creatures known to the public.

As such, if you want to observe a Gastornis in its natural habitat, check out Age of Mammals, Jurassic Park: Builder, ARK: Survival Evolved, and the famous Ice Age films!

Besides this, you’ll soon be able to admire a life-like, feathered Gastornis model at the Yale Peabody Museum!


Gastornis (Terror Bird)| Aunt_Spray via Getty Images

Gastornis was a proud inhabitant of prehistoric Europe, Asia, and North America. 

It is thought to have evolved in Europe and subsequently migrated to Asia and North America to conquer new territories!

As a flightless bird, Gastornis had small, undeveloped wings.

It had a massive skull, a large, tall beak, a short yet robust neck, and long legs.

It may have been a carnivore, an omnivore, or a herbivore; scientists haven’t discovered the full secret yet.

Here’s another thing you shouldn’t forget about Gastornis: It laid huge eggs, reaching 24 x 10 centimeters (9.5 x 3.9 inches)!

No wonder the adults grew so tall!


Is Gastornis a terror bird?

Gastornis is not a terror bird, as it’s not part of the Phorusrhacidae family of terror birds.

Is it Diatryma or Gastornis?

The genus was first called Gastornis, and its name still stands.

The Diatryma genus was described in the 19th century based on fossils belonging to a giant ground bird. 

Upon further research, scientists confirmed that they were, in fact, Gastornis remains.


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